# US Federal Holiday Working Day

> Checks a date against the OPM federal-employee holiday schedule and the US Saturday/Sunday baseline.

- Calculator id: `us-federal-working-day` · Category: Everyday Life (`everyday`) · Tool name: `check_us_federal_working_day`
- Canonical page: https://tttkmbb.com/everyday/us-federal-working-day · This document: https://tttkmbb.com/everyday/us-federal-working-day.md · JSON definition: https://tttkmbb.com/everyday/us-federal-working-day.json

## Purpose

Checks a date against the OPM federal-employee holiday schedule and the US Saturday/Sunday baseline.

**Use when:** You need US federal employee or federal-office holiday status for 2026-2027.

**Do not use when:** You need a state/local/private-employer/exchange calendar or an alternate federal work schedule without explicit in-lieu resolution.

## Example user requests

- Is 2027-07-05 a US federal working day?


## Input

| Parameter | Type | Unit | Required | Description |
| --- | --- | --- | --- | --- |
| `date` | date |  | required | Gregorian date in the pinned OPM 2026-2027 coverage. |

## Output

| Field | Type | Unit | Description |
| --- | --- | --- | --- |
| `territory` | string |  | US. |
| `territory_name` | string |  | United States. |
| `weekday` | string |  | Gregorian weekday. |
| `is_working_day` | boolean |  | True when the US Saturday/Sunday baseline is a weekday and no OPM federal holiday applies. |
| `day_type` | string |  | Regular weekday, regular weekend or OPM federal holiday. |
| `holiday_names` | string_list |  | OPM federal holiday names applying on the date. |
| `holiday_observed` | boolean |  | True when the date is the OPM in-lieu/observed date for a holiday whose actual date is a weekend. |
| `holiday_actual_dates` | string_list |  | Underlying statutory holiday dates for observed events. |
| `weekend_days` | string_list |  | CLDR Saturday/Sunday baseline. |
| `rest_day_policy` | string |  | OPM alternative work schedules need separate in-lieu resolution. |
| `calendar_scope` | string |  | Federal employees and federal offices only. |
| `calendar_profile` | string |  | us-opm-federal-holidays. |
| `source_quality` | string |  | Official OPM schedule and federal-law references. |
| `dataset_version` | string |  | Pinned OPM evidence package. |
| `sources` | list |  | Official OPM, federal guidance and legislation sources. |

## Formula

`is_working_day = US weekday baseline and no OPM federal holiday`

Apply the pinned OPM observed-date schedule on top of the CLDR US weekend baseline.

## Data Sources

- U.S. Office of Personnel Management Federal Holidays — https://www.opm.gov/policy-data-oversight/pay-leave/federal-holidays/ (government, published 2026-09-29)
- OPM Federal Holidays - In Lieu Of Determination — https://www.opm.gov/policy-data-oversight/pay-leave/work-schedules/fact-sheets/federal-holidays-in-lieu-of-determination/ (government_guidance)
- 5 U.S.C. 6103 — https://uscode.house.gov/view.xhtml?req=granuleid:USC-prelim-title5-section6103&num=0&edition=prelim (legislation)

Data freshness: `static`. OPM publishes annual federal schedules; refresh only after official review.

## API

- `GET https://tttkmbb.com/api/v1/calculate/us-federal-working-day?date=…`
- `POST https://tttkmbb.com/api/v1/calculate/us-federal-working-day` with JSON body `{"inputs": {…}}`
- Response: unified envelope (`success`, `request`, `result.values`, `result.units`, `sources`, `freshness`, `timestamp`, `next_actions`, `links`); see https://tttkmbb.com/docs/response-format.md
- Schema: https://tttkmbb.com/api/v1/calculators/us-federal-working-day · OpenAPI operationId `check_us_federal_working_day` in https://tttkmbb.com/openapi.json
- Authentication: none. Rate limit: fair use, see https://tttkmbb.com/docs/rate-limits.md.

## MCP

- Server: `https://tttkmbb.com/mcp` (Streamable HTTP, JSON-RPC 2.0, no auth)
- Tool: `check_us_federal_working_day` (dedicated) or `run_calculator` with `{"calculator_id": "us-federal-working-day", "inputs": {…}}`

## Example

- Observed Independence Day: inputs `{"date":"2027-07-05"}` → `{"is_working_day":false,"holiday_observed":true}`

```
GET https://tttkmbb.com/api/v1/calculate/us-federal-working-day?date=2027-07-05
```

## Limitations

You need a state/local/private-employer/exchange calendar or an alternate federal work schedule without explicit in-lieu resolution. Apply the pinned OPM observed-date schedule on top of the CLDR US weekend baseline. All values are computed from the formula above; no measurement or live data is involved.

## FAQ

**Does this cover US state holidays?**

No. It is limited to OPM federal employees and federal offices.

## Related

- [Add US Federal Working Days](https://tttkmbb.com/everyday/us-federal-add-working-days.md) — Offset using the same OPM evidence package.